The present invention relates to tungsten inert gas (TIG) welding and, in particular, to apparatus for sharpening the tungsten electrode used therewith to a needle-like point.
Within the welding industry, TIG welding is most commonly used during the welding of aluminum, chrome, copper, nickel, stainless steel, and high carbon steels. Depending upon the type of materials being welded and the application thereof, the best results are obtained via a proper selection of amperage and reverse or straight polarity to the electrode, the availability of a sufficient amount of inert gas (i.e. Argon or Helium) in the region of the weld, the maintenance of a uniform arc length, and the use of a finely-sharpened electrode.
While each of the mentioned factors, as well as others, can affect the weld quality, the latter factor or maintaining a sharp electrode presents an ongoing problem to the welder; especially during reverse polarity welding, since over time and use, the tip constantly loses its point and/or becomes contaminated with splattered material. The electrode then loses its ability to confine the arc and electric energy to the desired application site. Depending upon the material being welded, the criticality of this factor can vary, but for harder materials, such as stainless steel, it becomes especially important. In fact, in applications such as nuclear power plants, TIG welding is routinely done by teams of welders and in support of which some individuals do nothing other than make available sharpened electrodes to the welders so as to facilitate work output.
The tungsten electrodes used in TIG welding are most commonly manufactured in lengths of 3, 6, 7, 12 and 18 inches and diameters from 0.04 to 3/8 inch. Depending upon the length, the electrodes are oftentimes broken in half, before the ends are sharpened to the desired point. The electrode then being mounted in the hand-held welding holder.
Sharpening, in turn, presents a number of considerations, in that depending upon the work, either more or less taper may be desired. In all cases, however, it is desirable to maintain the point as close as possible to the concentric center to the electrode and to minimize surface imperfections, such as abrasions, etc. and which can affect the weld quality. Heretofore and most typically, the electrode have been sharpened using abrasive techniques so as to wear away the electrode in a tapered fashion relative to an abrading wheel of an appropriate grit. For example, one such device is sold by Hobart Inc. In use, the electrode is typically chucked into a hand drill and mounted to the apparatus relative to a grinding wheel so that upon rotating the electrode and passing the grinding wheel over the electrode, a tapered point is eventually achieved. The problem with this method and apparatus, however, is that the sharpening equipment is rather costly and the process rather time consuming.
Yet another methodology that has been developed for sharpening such electrodes is a chemcial technique developed by Kemsharp Inc. and which relies upon the heating of the electrode before immersing and drawing the electrode from a chemical bath. Given the cost of the chemical bath and its limited useful life, this methodology, too, does not represent the optimal solution.
In order to overcome the limitations of the foregoing sharpening methodologies, the present invention was developed and which provides a means for flame sharpening the electrode to a properly profiled point, in less than a minute, using available equipment. In general terms, it achieves this end by mounting the electrode in acute relation to the flame of a cutting torch while rotating the electrode so as to controlably vaporize the electrode to a desired point.
While flame sharpening techniques have been employed in various technologies, for example glassworking, it is not believed that heretofore such techniques have been applied in the welding arts and especially not in the fashion or with the apparatus presently contemplated. One reference, however, that applicant is aware of from the glassworking arts is U.S. Pat. No. 2,659,181 and wherein one or more flames from an oxy-gas device are applied generally orthogonally to a mechanically preformed stylus, before rotating the stylus and progressively moving it through the flames so as to produce a heat-glossed surface and a rounded tip, such as might be used with a stylus of a phonograph cartridge.
As should be apparent, however, the present invention is intended to produce a relatively finer and more tapered point and which it achieves via substantially different apparatus. The above objects, advantages and distinctions, among others, as well as the construction of the present invention will, however, become more apparent upon reference to the following description thereof with respect to the appended drawings. Before referring thereto, though, it is to be recognized that the following description is made by way of reference to the presently preferred embodiment only, but which is not intended to be limiting of the scope thereof.